Utilization by the Chick of Vitamin A from Different Sources I. Crystalline Carotene, Crystalline Vitamin A Acetate, and “Black Cod” Liver Oil

Evaluation of Vitamin Requirement Data

“…Plasma vitamin A concentration of turkeys as related to log dietary concentration of vitamin A activity. Results very similar to those of Castano et al (1951) have been obtained with the turkey by Gurcay et al (1950). The broken lines represent the corresponding lines for chicks taken from Fig.…”

“…Apparently the slope of the cryptoxanthin growth response line more consistently resembles that of vitamin A rather than that of /3-carotene. Castano et al (1951) have compared crystalline carotene, vitamin A acetate and a cod liver oil for effects upon growth, plasma vitamin A and liver vitamin A in chicks. It was pointed out by Guilbert et al (1939) that there were indications of a widening in the potency ratio of vitamin A to carotene as the levels of intake increased.…”

Carotenoid vitamin A precursors and analogs in foods and feeds

“…The vitamin A activity, as in the case of the rat, must be evaluated in relation to dietary dosage. At lower levels of feeding, where the criterion (33,167) is growth, it is essentially equal to the activity found in rats, a ß-carotene to vitamin A weight ratio of 2:1. Based on liver storage (33,167) of vitamin A, where higher than minimum maintenance levels are fed, a marked reduction in efficiency of conversion takes place.…”

“…At lower levels of feeding, where the criterion (33,167) is growth, it is essentially equal to the activity found in rats, a ß-carotene to vitamin A weight ratio of 2:1. Based on liver storage (33,167) of vitamin A, where higher than minimum maintenance levels are fed, a marked reduction in efficiency of conversion takes place. Data from this laboratory (148) demonstrate that over a feeding range of 1000 to 5000 IU of vitamin A per pound of ration in the form of dry stabilized ß-carotene or dry stabilized vitamin A palmitate, the vitamin A product consistently provides for 2.5 times the liver stores of vitamin A, as compared to the equivalent unitage from ß-carotene, an effective weight basis ratio of 5 mg of ß-carotene: 1 mg of vitamin A.…”